Field of the Invention
The present invention relates to a laser machining apparatus for machining a workpiece such as semiconductor wafer.
Description of the Related Art
A semiconductor wafer having a device such as IC formed in each of the areas partitioned by scheduled division lines is machined, for example, by a laser machining apparatus, thus being divided into a plurality of device chips, each corresponding to a device. Such a laser machining apparatus generally includes a chuck table and a laser irradiation unit. The chuck table sucks and holds a semiconductor wafer or other workpiece. The laser irradiation unit irradiates a laser beam. In order to machine a workpiece with this laser machining apparatus, a laser beam is irradiated from the laser irradiation unit while at the same time relatively moving the laser irradiation unit and the chuck table in a direction parallel to the scheduled division lines (hereinafter also referred to as machining feed). This allows a laser beam to be irradiated along the scheduled division lines of the workpiece sucked and held by the chuck table, thus machining the workpiece.
Incidentally, a machining method is commercially available which machines a workpiece by reciprocally moving the laser irradiation unit and the chuck table in a direction parallel to the scheduled division lines for enhanced machining efficiency of a laser machining apparatus such as the one described above. With this machining method, for example, the relative movement (machining feed) of the laser irradiation unit and the chuck table is stopped after the end of machining in the forward trip. Next, the irradiation position of the laser beam is set at the extension of the scheduled division line to be machined in the backward trip by relatively moving the laser irradiation unit and the chuck table in a direction perpendicular to the scheduled division lines (hereinafter also referred to as indexing feed). Then, machining in the backward trip is initiated.
Further, a new technology that focuses on the amounts of time required to stop machining feed and required for indexing feed (refer, for example, to Japanese Patent Laid-Open No. 2012-161799) has been proposed. This technology stops machining feed and conducts indexing feed in parallel, thus reducing the amount of time required for indexing feed to substantially zero and shortening the amount of time until next machining for enhanced machining efficiency.